/*
 * Copyright (C) 2007 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.android.dx.rop.code;

/**
 * Interface for "advice" passed from the late stage of translation back to the
 * early stage. This allows for the final target architecture to exert its
 * influence early in the translation process without having the early stage
 * code be explicitly tied to the target.
 */
public interface TranslationAdvice {

	/**
	 * Returns an indication of whether the target can directly represent an
	 * instruction with the given opcode operating on the given arguments, where
	 * the last source argument is used as a constant. (That is, the last
	 * argument must have a type which indicates it is a known constant.) The
	 * instruction associated must have exactly two sources.
	 * 
	 * @param opcode
	 *            {@code non-null;} the opcode
	 * @param sourceA
	 *            {@code non-null;} the first source
	 * @param sourceB
	 *            {@code non-null;} the second source
	 * @return {@code true} iff the target can represent the operation using a
	 *         constant for the last argument
	 */
	public boolean hasConstantOperation(Rop opcode, RegisterSpec sourceA,
			RegisterSpec sourceB);

	/**
	 * Returns true if the translation target requires the sources of the
	 * specified opcode to be in order and contiguous (eg, for an invoke-range)
	 * 
	 * @param opcode
	 *            {@code non-null;} opcode
	 * @param sources
	 *            {@code non-null;} source list
	 * @return {@code true} iff the target requires the sources to be in order
	 *         and contiguous.
	 */
	public boolean requiresSourcesInOrder(Rop opcode, RegisterSpecList sources);

	/**
	 * Gets the maximum register width that can be represented optimally. For
	 * example, Dex bytecode does not have instruction forms that take register
	 * numbers larger than 15 for all instructions so DexTranslationAdvice
	 * returns 15 here.
	 * 
	 * @return register count noted above
	 */
	public int getMaxOptimalRegisterCount();
}
